Thippeswamy Ramakrishnappa

In situ reduction and functionalization of graphene oxide with L-cysteine for simultaneous electrochemical determination of cadmium(II), lead(II), copper(II), and mercury(II) ions

One pot reduction and functionalization of graphene oxide (GO) with L-cysteine (L-cys-rGO) at the edges and basal planes of the carbon layers are presented. The L-cys-rGO was characterized by X-ray diffraction studies (XRD), X-ray photoelectron spectroscopy (XPS), attenuated infrared spectroscopy (ATIR), and Raman spectroscopy. The surface morphology was studied by scanning electron microscopy (SEM) and transmittance electron microscopy (TEM). The L-cys-rGO was further utilized for the simultaneous electrochemical quantification of environmentally harmful metal ions such as, Cd2+, Pb2+, Cu2+ and Hg2+. Detection limits obtained for these metal ions were 0.366, 0.416, 0.261 and 1.113 μg L−1 respectively. The linear range obtained for Cd2+, Cu2+ and Hg2+ was 0.4 to 2.0 μM and for Pb2+ was 0.4 to 1.2 μM. The detection limits were found to be less than the World Health Organization (WHO) limits. The developed protocol was applied for the determination of the above metal ions in various environmental samples and the results obtained were validated by atomic absorption spectroscopy (AAS).

Synthesis and Characterization of CeO2 Nanoparticles via Solution Combustion Method for Photocatalytic and Antibacterial Activity Studies.

CeO2 nanoparticles have been proven to be competent photocatalysts for environmental applications because of their strong redox ability, nontoxicity, long-term stability, and low cost. We have synthesized CeO2 nanoparticles via solution combustion method using ceric ammonium nitrate as an oxidizer and ethylenediaminetetraacetic acid (EDTA) as fuel at 450 °C. These nanoparticles exhibit good photocatalytic degradation and antibacterial activity. The obtained product was characterized by various techniques. X-ray diffraction data confirms a cerianite structure: a cubic phase CeO2 having crystallite size of 35 nm. The infrared spectrum shows a strong band below 700 cm−1 due to the Ce−O−Ce stretching vibrations. The UV/Vis spectrum shows maximum absorption at 302 nm. The photoluminescence spectrum shows characteristic peaks of CeO2 nanoparticles. Scanning electron microscopy (SEM) images clearly show the presence of a porous network with a lot of voids. From transmission electron microscopy (TEM) images, it is clear that the particles are almost spherical, and the average size of the nanoparticles is found to be 42 nm. CeO2 nanoparticles exhibit photocatalytic activity against trypan blue at pH 10 in UV light, and the reaction follows pseudo first-order kinetics. Finally, CeO2 nanoparticles also reduce CrVI to CrIII and show antibacterial activity against Pseudomonas aeruginosa.

Recent Progress on Pyrazole Scaffold‐Based Antimycobacterial Agents

New and reemerging infectious diseases will continue to pose serious global health threats well into the 21st century and according to the World Health Organization report, these are still the leading cause of death among humans worldwide. Among infectious diseases, tuberculosis claims approximately 2 million deaths per year worldwide. Also, agents that reduce the duration and complexity of the current therapy would have a major impact on the overall cure rate. Due to the development of resistance to conventional antibiotics there is a need for new therapeutic strategies to combat Mycobacterium tuberculosis. Subsequently, there is an urgent need for the development of new drug candidates with newer targets and alternative mechanism of action. In this perspective, pyrazole, one of the most important classes of heterocycles, has been the topic of research for thousands of researchers all over the world because of its wide spectrum of biological activities. To pave the way for future research, there is a need to collect the latest information in this promising area. In the present review, we have collated published reports on the pyrazole core to provide an insight so that its full therapeutic potential can be utilized for the treatment of tuberculosis. In this article, the possible structure–activity relationship of pyrazole analogs for designing better antituberculosis (anti‐TB) agents has been discussed and is also helpful for new thoughts in the quest for rational designs of more active and less toxic pyrazole‐based anti‐TB drugs.

Hydrothermal synthesis of 2D MoS2 nanosheets for electrocatalytic hydrogen evolution reaction

Nanostructured molybdenum disulfide (MoS2) is a very promising catalyst for producing molecular hydrogen by electrochemical methods. Herein, we have designed and synthesized highly electocatalytically active 2D MoS2 nanosheets (NS) from molybdenum trioxide (MoO3) by a facile hydrothermal method and have compared their electrocatalytic activities for hydrogen evolution reaction (HER). The electrochemical characterization was performed using linear sweep voltammetry (LSV) in acidic medium. The MoS2 NS show a HER onset potential at about 80 mV vs. reversible hydrogen electrode (RHE) which is much lower than MoO3 (300 mV). The MoS2 NS and MoO3 show a current density of 25 mA cm−2 and 0.3 mA cm−2, respectively at an overpotential of 280 mV vs. RHE. The MoS2 NS showed an 83 times higher current density when compared to MoO3. The Tafel slopes of the MoS2 NS and MoO3 were about 90 mV per dec and 110 mV per dec respectively. This suggests that MoS2 NS are a better electrocatalyst when compared to MoO3 and follow the Volmer–Heyrovsky mechanism for HER.

Hydrogen generation and degradation of trypan blue using fern-like structured silver-doped TiO2 nanoparticles

TiO2:Ag nanoparticles have been successfully prepared at 120 °C in one day using an ionic liquid assisted hydrothermal method with methoxyethyl methyl imidazolium methanesulfonate as the ionic liquid. The obtained product was characterized using various techniques. The XRD pattern indicated the formation of TiO2:Ag nanoparticles, the average crystallite size was found to be 40 nm. XPS confirmed the formation of TiO2:Ag nanoparticles. The UV-Vis spectrum indicated a maximum absorbance at 362 nm which is red shifted compared to nano-sized TiO2. The surface morphology was analyzed using SEM, which shows a leaf-like structure for the TiO2:Ag nanoparticles. TEM images showed almost elliptically (rice pellet) shaped nanoparticles with an average particle size of about 60 nm. The EDS spectrum revealed the presence of Ti, O and Ag with atomic percentages of 42.6, 43.7 and 2.3%, respectively. The TiO2:Ag nanoparticles generate 2230 μmol H2 per 1 g of photocatalyst in 2.5 h via the water splitting reaction. They also show good photocatalytic activity in the degradation of trypan blue.

Non-Enzymatic Amperometric Determination of Glucose by CuO Nanobelt Graphene Composite Modified Glassy Carbon Electrode

We have successfully developed for the first time an electrochemical sensor for glucose by using a simple and effective design of growing CuO nanobelts graphene composites (CuO@G). The as prepared composites were characterized by X-ray diffraction studies (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The prepared composite material exhibits higher electrocatalytic activity for the oxidation of glucose compared to chemically reduced graphene (C rGO) and bare CuO nanobelts. The optimized protocol has linearity with current response for glucose concentration in the range 0.5-6.5 μmol L−1 and detection limits were found to be 0.05 μmol L−1 (3σ). The method exhibits good reproducibility and selectivity towards glucose in the presence of other electro active compounds that are normally present in blood serum like dopamine, ascorbic acid, uric acid and sodium chloride. The protocol has been successfully applied for glucose determination in clinic human blood serum samples.

Superior activity of the CuS–TiO2/Pt hybrid nanostructure towards visible light induced hydrogen production

A CuS–TiO2 hybrid nanostructure has been synthesized and employed for photocatalytic hydrogen production under UV-Vis light using Na2S and Na2SO3 as the sacrificial agents. The remarkable hydrogen production recorded for the CuS–TiO2 heterostructure was 458 μmol h−1 g−1 and for CuS–TiO2/Pt was 746 μmol h−1 g−1. The corresponding apparent quantum yield values are 1.01% and 1.55%. The addition of Pt to the hybrid structure acts as a metallic sandwich between two semiconductors CuS and TiO2 which assist in charge separation.

Electrochemical detection and photochemical detoxification of hexavalent chromium (Cr(VI)) by Ag doped TiO2 nanoparticles

We are proposing a simple, green and one pot ionothermal protocol for the synthesis of Ag doped TiO2 nanoparticles. The prepared material was characterized by various spectroscopic techniques like P-XRD and XPS and then the electrocatalytic reduction and photocatalytic detoxification ability of the material towards Cr(VI) were explored. Amperometric studies showed a linear range from 0.1 to 3.1 μM, and limits of detection and quantification of 0.01 μM and 0.033 μM, respectively. The material also showed better photochemical reduction of Cr(VI) in sunlight compared to UV light. About 90% reduction of Cr(VI) to Cr(III) was observed in 120 min in sunlight whereas 88% reduction was obtained in UV light in the same time. The Ag doped TiO2 nanoparticle modified glassy carbon has been used for electrochemical monitoring of Cr(VI) in natural water samples.

Enhanced photocatalytic hydrogen production from Y2O3/TiO2 nano-composites: a comparative study on hydrothermal synthesis with and without an ionic liquid

Hetero-junction Y2O3/TiO2 nano-composite (NC) photocatalysts were synthesized using a conventional hydrothermal method (Y2O3/TiO2 NC(HM)) and an ionic liquid assisted hydrothermal method (Y2O3/TiO2 NC(ILAHM)). The composite nature and physico-chemical properties of the photocatalysts prepared through both routes as a function of thermal treatment were investigated via thorough characterization. A comparison of the photocatalytic hydrogen production via water splitting is provided. It was found that the concentration of Y2O3 in the TiO2 matrix and the post thermal treatment have obvious effects on the hydrogen production activity, and they were fine-tuned for enhancement of the hydrogen production. The required synergy between Y2O3 and TiO2 was found to occur at an optimum concentration of 25 wt% Y2O3 in the TiO2 matrix, with the sample prepared at 400 °C for 1 h. The optimized NC i.e. 25 wt% Y2O3/TiO2 NC(ILAHM) produced a promising hydrogen evolution of 1380 μmol g−1 that was almost 2-fold the production from 25 wt% Y2O3/TiO2 NC(HM). The enhancement was attributed to the porous surface morphology, higher surface area and quantum yield of the NC prepared using the ionic liquid assisted hydrothermal method.

Ionic liquid-assisted hydrothermal synthesis of TiO2 nanoparticles and its applications towards the photocatalytic activity and electrochemical sensor

This work reports the synthesis of TiO2 nanoparticles via ionic liquid-assisted hydrothermal method at 130 °C for two days. The obtained product was characterised by various techniques. The X-ray diffraction data reveal the anatase phase TiO2 nanoparticles with crystallite size 37 nm. The Fourier transform infrared spectrum shows a band at 400 cm−1 due to Ti–O–Ti stretching vibration, in addition to the presence of ionic liquid. The UV–Vis spectrum of TiO2 nanoparticles shows an absorption band at 314 nm which indicates a blueshift compared with that of bulk TiO2. The transmission electron microscopy images show almost spherical-shaped nanoparticles with an average diameter of 40–80 nm. TiO2 nanoparticles exhibit excellent photocatalytic activity for the degradation of trypan blue, and also help in the reduction of Cr+6 to Cr+3. TiO2 nanoparticles modified glassy carbon electrode exhibits better electrocatalytic oxidation towards dopamine compared with bare glassy carbon electrode.